In a line-impact, dot-matrix printer (LIDM printer), the distance between the impact hammers and the platen has an effect on the print quality. Since this type of printer can type on paper forms of various thicknesses, it is often necessary to adjust the distance between the impact hammers and the platen for optimum printing performance. If the distance is too large, the impact hammers do not strike the ink ribbon with enough force to transfer the ink from the ribbon to the paper. If the distance is too small, there will likely be smudging on the paper due to the hammers pressing the ribbon against the paper even when the hammers are retracted.
In conventional LIDM type printers, the distance between the platen and the impact hammers is adjusted manually. Adjustment typically begins by setting a large distance and then reducing the distance until ribbon smudging appears on the paper. The distance is then increased slightly until the smudging disappears. Arriving at the optimal distance requires some experience on the part of the user, and the process must be repeated each time a new supply of paper is loaded into the printer.
Much time would be saved if the adjustment of the distance between the platen and the impact hammers could be done automatically, without the user manually moving either the platen or impact hammers. Additionally, consistent printer performance would inevitably result as well. The problem is developing an automatic approach for determining and setting the optimal print gap distance.